Improvement in steam-engines



NPETERS. PHDTO-LITHOGRAPHER, WASHINGTON, D C.

UNITED STATES v oEARLEs E. .EMERYQOE BROOKLYN, NEW YORK.

IM PROVENI ENT I'N STEAM-ENGINES.`

Specification forming part of LettersPatent No. 70,707, dated November 12,1867.

To all whom it may concern:

Be it known that I, CHARLES E. EMER'Y., of Brooklyn, in the county of Kings and'State of New York, have discovered and invented certain new and useful Improvements in Steam- Engines; and I do hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawings,'making part of this specication.

It is a patent fact that the best steam-engines utilize onlyT one-tenth to one-ninth of the heat in the steam used. Scientific men speak of the loss as unexplained, and state vthat the steam-engine is yet in its infancy, and that no considerable'improvement has been made in it since the days of Watts. In spite of all the efforts of inventors to economize fuel, the fact still stares them in the face that nearly ninety per cent. of the steam is wasted.

Many experiments have been made with superheated steam, and thatl principle may undoubtedly be carried with economy as far as mechanical means will allow. Most attention, however, has probably been paid to the enormous prots promised by theory from the expansion of steam; but it is well known that the expected gains from this source have never been practically realized. Compared withl full-stroke, the theoretical gain by cutting off steam at half-stroke is sixty-nine per cent. vAt quarter-stroke it is one hundred and kthirty-eight per cent., and increases with the grade of expansion. Notwithstanding this, it is doubtful if a gain 'of fifty per cent. has ever been obtained in practice, which could all be attributed to expansion alone, rather than to differences in pressure, superheating, or some circumstance, often used .in connection with expansion, and for which that principle has the credit,`but which, in fact, increases proportionably the economy of the power nearly as much at one grade of expansion as another. Though many 'will deny this, the small percentage of the theoretical performance utilized in the best steamengines, using expansion in the most approved manner, shows that there is a discrepancy somewhere. Still it is to the expansion of steam that we should look for further economy. f A steam-engine is simplyI a vheat-engine. Water takes up the heat; steam is'tlie result.

E If steam be expanded, work is done. A quantity of heat the mechanical equivalent of the work done disappears, and leaves its vehiclethe water-in its original condition.. In other words, steam is condensed. Theoretically, wel

should be able to carry on lthe expansion till the heat force is all utilized and the steam all becomes water. Practically, the steam-pressure can never be economically reduced below that necessary' to equilibrate the resistances incident to the engine itself. Up to this point, then, we should expect gain; still we do' not in practice realize it.

Modern discoveries in science have pointed out no reason why this is so. They only show that the pressure must reduce faster than the ordinates of a hyperbolic curve, on account of condensation due' to work donev and varying Then, since the theoryof extemperature. p pansion is so conclusive, and we are not able to obtain results in accordance therewith,

i should we not look carefully at the practical side of the question, and strive to find, in thel materials used, or in their form, disposition, or movements, some fault to which may be .at-1. tributed the losses.l y First, we must allow that a steam-'engine cylinder appears to hold;Y the steam, and that the operation of the valvegear and piston and its connections undoubtedlypermits its expansion, and transmits the'y force derived therefrom to the desired point'. I say the cylinder appears to hold the steam.' Now, what is steam? We may say water which, by the action of heat, has hadwork done upon its particles, separating andagitatl ing them. Less literally, it is 'simply water and heat. Does the cylinder holdboth? Put your hand on it and see. Ahi your flesh is not Wet, but is burned-that is, the cylinder holds water, but not heat. It is, in fact, ready, at the rst opportunity, to give away the very force we wish to utilize. Your hand robbed the cylinder of a little heat, the cylinder robbed the inclosed steam, leaving a little useless water. However:7 we expect loss from the outside, and guard against it by covering of felt or similar material.

place on the inside. There is nothing but steam.there,you say. Why was yourhand burned? Simply because it was colder than the metal. the.v steam ever coolerl than the Let us linquire'if any similar loss can take` metal? Certainly it is, at the very time it is going out'of the cylinder,'and can carryall the heat it receives away to wast-e.

The differences in temperature inside a steamcylinder during a double stroke of the piston are very considerable. The steam enters usually at near the boiler pressure and temperature, and if it be expanded the Vtemperature necessarily falls from the time the cutoff valve closes to the end of the stroke. When the exhaust valve opens, the temperature again falls to that due to the back pressure.' For example, if steam, admitted to the cylinder at a pressure of thirty-five pounds per square inch above the atmosphere, be cut 0E at a quarter of the stroke from the beginning, and at the end exhausted into a condenser against a back pressure lof two pounds, its temperature during the first quarter of the stroke will, in round numbers, be 2800 Fahrenheit, and gradually fall to 2050 at the end of the stroke, when, after the exhaust, it will be `suddenly reduced to 1300, remaining so during whole return-stroke. The metal of the cylinder at iirst necessarily becomes nearly as hot as the boiler-steam; but when the communication with the boiler is shut ofi' the -temperatiufe of the confined steam at the end of the stroke becomes 7 5O lower than that of the metal, and the difference increases to'l500 when the exhaust takes place, and remains so during the entire return-stroke.

Tyndall has shown that aqueous vapor is a very powerful absorbent of radiant heat. When, then, as we have shown, the temperature ofthe metal of a steam-cylinder is so much higher than that of the inelosed steam, a great deal of heat' must be radiated from the metal, absorbed by the steam, and carried with it out of the cylinder. The heat radiated from the metal must be resupplied from the-incoming boiler-steam to adjust the temperatures.

When the boiler furnishes saturated steam, since that is its maximum density, as steam, at the point' of saturation, no heat can be taken from it without producing condensation. Hence the heat required to reheat the cylinder and that transmuted into Work both produce condensation. A portion of the steam yields up its latent heat and collapses from the volume of steam to that of water at the same temperature. So long as the steam -valve is open new steam enters to keep up the pressure. Hence it often occins, in practice, that twice as much steam is used as is required by calculation. There is nothing strange in this if the metal of the cylinder, at the beginning of each stroke, is cool enough to condense about half the steam that enters. With superheated steam the effect is similar, though no condensation need take place. The free superheated goes to supply that .necessary to reheat the cylinder and perform the Work. This decreases the volume, and While the steam-valve is open more steam flows in to keep up the pressure. The density is thereby increased, and, like saturated r steam, it reand keep up the initial pressure.

quires a larger quantity of boiler-steam to maintain the initial pressure and temperature.

Let us now carefully follow the steam through the cylinder of an engine, explaining the changes which take place upon the principles above stated. The metal of the cylinder being somewhat cooled during a previous stroke, in manner pointed out, sufficient steam enters not only to fill the space, but to reheat the metal The steam is shut off, expansion takes place, and soon the temperature of the steam becomes lower than that of the cylinder. The metal, in turn, becomes the heater. It re-evaporates whatever water is 4in contact with it, and radiates its heat into the steam, and thus superheats it, or re-evaporates the suspended watery par ticles of condensation, as the case maybe. All the heattaken from the metal during the steam-stroke is utilized, for it increases the volume or pressure of the steam, and thereby produces a dynamic effect. on the piston. When the exhaust takes place, however, all the heat required to re-evaporate the Water on the surfaces, all that can be radiated from the metal and absorbed by the steam, and that received by the steam by direct attrition against the heated sides of the cylinder and narrow ports during the time of the whole return-stroke, is carried away out of the cylinder, and, for the purpose of Work, entirely wasted. vAll this heat has to be supplied at every stroke, to be again and again wasted and resupplied. The lost heat is furnished by an additional quantity of steam, which unfortunately enters and leaves the cylinder Without showingits presence by an increase of pressure, wherefore calculations to determine the quantity of steam used are necessarily incorrect when founded, as is usual, upon the terminal pressures, shown by indicatordiagrams.

In the famous Erie expansive experiments it was found that at the higher grades of expansion from forty to forty-tive per cent. more steam entered the cylinder than was accounted for by calculation from the terminal pressiue. About eight lper cent. of this was condensed to furnish heat for the Work; the rest was absolutely wasted. Bonne mentions that in one of the noted double-cylinder pumpin engines in En gland thirty -three per cent. of the steam was unaccounted for by the indicator. In small enginesthe discrepancy often amounts to two-thirds of the steam used.

It would seein to be impossible for an engine to work when so much of the steam is condensed in the cylinder. Now, Tyndall has shown that a good absorbent is necessarily also a goodradiator. So, when -steam enters a cooled cylinder, though some wat-er may be condensed on the surfaces, like dew, the Whole body of the steam is also chilled by radiation, and the condensed water left suspended in the steam in a fog or cloud. A small quantity of water may possibly be held invisibly suspended, like the aqueous vapor inthe atmosphere; but larger amounts undoubtedly form a cloud, from which, when the abstraction of heat is carried sufficiently far, water probably drops like rain.

The quantity of steam necessary-to reheat the cylinder shouldfincrease slightly with the grade of expansion, for the'metal is exposed toa temperature -lower than its own for a' larger portion of each stroke. But since less steam enters the cylinder at the higher grades, not only the quantity required for reheating, but also that lcondensed for the work, must forma larger proportion of the whole quantity.v In other words, the percentage of water con` .densed and unaccounted for by the indicator must increase with the grade of expansion, at least np to a point where the metal is' heated and cooled all that is possible in the time of a double-stroke. i t l l Inhaccordance with the principles above adopted to explain the losses in steam-engine,

we may account for the' gains which are ob to as a model of economy, and an example of the efciency of extremeV expansion. Others adopt the same pressure of steam and the same grade of expansion,but do not realize the'same' degree of economy. yWhy is this?` Now, Cornish boilers are very economical; but that will not account for allthe gain; On the principle above stated, we 1ind',first, that 'Cor-v nish engines are generally large, and for that reason economical; But more than this, they are single-acting. The hot boiler-steam never touches the coolest portions ofthe cylinder. It enters only at the top, and'presses down thev piston until the beam and heavy pump-rods are put in motion. The steam is then shut off, and the stroke completed by expansion.' t As the steam lowers in temperature'the surround ing-metal is correspondingly cooled; The return-stroke is accomplished by the weight of the pump -rods, and the piston simply displaces the steam from one end of the cylinder to the` The up'- l other through the equilibrium-valve. per or hot end of the cylinder is'neaverin connection with the condenser, and the cool 'end is at no timein direct communication with the boiler. 'Is it strange that greater economy canfbe attained, using such an instrument as this, yrather than a double-acting cylinder,

each end of `which'must be heated and cooled at vevery stroke? Again, the double-cylinder engine is consid#v ered very economical, andy properly so, for the small cylinder is never in communication with vordinary'double-acting engine.

the condenser.A The heat radiated from itis utilized on the large'piston, which standslike a screen to prevent its going entirely to waste.

4Viewing the matter in this light, vitjis probable that the economy of the-present double-cylinder engine could be increased bymaking less difference in the size of the cylindersl than is usual. l Y

- Great dierences of opinion exist as to what i'sthe most economicalpoint of cut-off in the undoubted gain withinreasonable'limitswhen the' higher grades of expansion have the bene` fit of higher pressure steam than the vlower grades, which is the only practical way of testing-the matter when doing the same-work in the same enginel and with the same piston speed." But moderate expansionists say that they are'entitled to as high a pressure of` steam as i'sused in any case, and that they can there- .by employa smaller engine with no' greater loss, than is .compensatedl for by. diminished first cost `and increased simplicity 'and rehability. The point about steam-pressure is lwell ',taken; vbut they forget that when `doing the same work with the same pressure of steam increased.- expansion not only necessitates a larger engine, but ,brings the economy due, as

above explained, to a larger 'engine 19er se. Itv 'is believed, therefore, thatl the views 'of the non expansionists'- are not upheld by' facts: There is,^however, a' limit to the application of the principle of expansion in engines as at presentconstructed, thebest, as has already been said, utilizing only one-tenth ofthe heat;

'I have above stated my theory fully, and have given some examples of its practical ap'- plication. Still, zmany 'may doubt that a cause apparently so small can produce such large and injurious effects; I would, however,call

'attention' to the fact' that Tyndall, when ex-` perimenting withV the very things that we have been discussing-viz., the-vapor of 'water `and radiant heat-#made discoveries still more incredible. He found that the invisible aqueous vapor present at all times kin the atmosphere hadseventy times the absorptive effectonradiant heat of dry air'. Any person who will carefully read his remarks on this subject; in connection with a'careful study of the changes of temperature that occur in a, steam-cylinder, which. in Afact confines `a kind of aqueous vapor Within radiatin'gsurfaces', will, I think, agree with me as to the naturel of the losses which are found in practice. K l

To prevent theseA losses,' I long ago proposed to make the interior surfaces of a steam-cylinder' of a poor conductorv or poor radiatorv of heat; but I found-that Tyndall had shown that a poor radiatora polished' surface, for instance-becomes a good one when a good ra'- cannot be lost, and less steam will be re-l There is anv quired to reheat the surface. By using a poor conductor, with lowspecific heat, the benefit shouldbe still moremarked. After carefully considering the` subject, my convictions were so strengthened by the considerations hereinbefore expressed, and by mathematical calculations, that I tried vthe matter practically. After some preliminary7 though encouraging, experiments with incomplete apparatus, I constructed two cylinders of like dimensions, one of glass, the other of iron, in such a manner that either couldbe attached to a valve which regularly admitted steam from-.a boiler to the cylinder, and permitted its exhaust into a condensingcoil lying in a -tub of water. The capacity of the two cylinders was made exactly the same, as was shown bytransferring waterfrom one to the other. When put, in turn, in the condition of a steam-engine cylinder, the. iron cylinder used twice as much steam as the glass one, shown by the fact that twice the quantity of water came through the condensing-coil for the same number of movements ofthe valve. Steam of the same pressure was used in both cylinders, and the experiments 4were many times repeated, with substantially the same results. This settled the question. The glass cylinder in that case saved half the steam. With more expansion I expect still greater gains. A large proportion of the theoretical saving promised by extreme expansion may perhaps be realized. Whether my theories be right or wrong, I have at least demonstrated the practical value of non-conducting material for the interior surfaces of steam-cylinders. i

- Popularly speaking, in relation to heat, all materials are divided into two classes-conductors7 and non-conductors.7 The metals constitute the` first class, ybut differ among themselves in'conducting-.powen Thus copper and compounds in which it enters largely, such as brass, conduct heat less freely than silver, but better than iron. Other-metals conduct heat less freely than iron. l For instance, lead and German silver have only from `threefourths to one-half its conductingLpower, and" bismuth has but about one-sixth.' Substances such as glass, porcelain, lire-brick, marble, and stones are known as non-conductors, and many of them have but about one-thirtieththe conductingpower of iron. Cast-iron is almost universally employed in the construction of steam-cylinders, and it has lower conductingpower than brass or any other substance now practically used for the purpose. i

The object of `my invention is to produce economy in the steam-engine. I accomplish this by, 'and my invention consists in, lining or coating the interior surface of the cylinders of steam-engines with glass, porcelain, enamel, or equivalent material. VI also propose to construct the whole cylinder of a poor conductor,

and have made changes in the form of steamengine cylinders and pistons, whereby certain portions of the surfaces that cannot always be conveniently lined may be protectedfrom direct radiation. I

For the purposes of my invention one ma-` terial used, as above expressed, is the equivalent of another whenfit conducts heat less freely than cast-iron and the application of the words poor conductor of heat77 and similar expressions, as herein used, is limited to such materials as conduct heat less freely than cast-iron.

In the drawings, Figure 1 is a longitudinal sectionof an ordinary steam-engine cylinder, and shows a poor conducting-lining applied to the Whole interior except the wearing-surfaces. Fig. 2 isa-transverse section of the same. Fig. 3 is'a longitudinal section. of the same cylinder altered so that the steam. is

displaced from the wearing-surfaces into the y protected ends by blocks on the piston. Fig. Llis a transverse section of the same. y Fig. 5 is a longitudinal section of a steam-cylinder containing a long plunger-piston, more particularly described hereinafter. Fig. 6 is a trans verse section of the same. Fig. 7 is an end view, Fig. 8 is a horizontal section, and Fig. 9 is a side view, of a steam-cylinder of the or` Vdinary form, with all the interior surfaces lined, and some peculiarities of construction, hereinafter. described. Fig. 10 isa vertical cross-section, and Fig. 1l is `a vertical transversesection, of another cylinder, hereinafter described. Figs. 12 and 13 are similar views materials which conduct heat slowly that can, be applied as a protecting-lining `to steam-en` gine-cylinders; but all of them cannot'be used for the surface upon which the piston rubs.

Figs. l and 2 are intended'to show what propor-V tion'of the radiating-surfaces to which steam is exposed in an ordinary steam-cylinder may be covered by a material not adapted for a' rubbing-surface.

By reference to the drawings, it will be seen that the lining or protecting material .fr .r covers the whole interior surface of the steamports (l (l from the base of the cylinder to or nearly to the valve-faces. It is placed on the inside of both cylinder-heads B and B', onboth sides of the piston A', and lines the clearancespace, which extends from the heads of f and g, where thewearing-surface of the cylinder commences. In a puppet-valve engine the interior of the nozzles and the disks of the valve would be covered. On this plan alarge part of the metal surfaces is left unprotected; but the exposed wearing-surface from j' to g forms a less proportion ofthe whole surface:

in cylinders of the same capacity, the larger the diameter and shorter the stroke.

Figs. 3, 4, 5, and 6 represent plans by which direct radiation is prevented from the metal wearing-surfaces into the main body of thev themain body of the steam from opposite the wearing-surfaces into the ends G G, which are lined, as shown. Steam is admitted by making the ports C O in' the ends G G, or by cutting off Vone side of the blocks. J and K are shown at F F. A plan of protecting the pston is also shown in Fig. 3, more useful for trunks with large surfaces than for ordinary piston-rods. A pipe, b, section in red, of about the length of the stroke, surrounds the rod a, and is secured at one end to the inside of head B. The block J has a hole in it, which works over the pipe when the piston moves in that direction. The pipe b is made either of poor conducting material, or is covered with such, at least on the outside, and therefore cuts off radiation to and from the rod and the main body of the surrounding steam. The surfaces of rod and hole in J may be protected also, if desired. The pipe b may also be se,-

cured to the piston, and run into an annular space between the rod and a hole in cover'B.

In Figs. 5 and 6 the piston A is, in fact, a plunger, something more than the length of the stroke, turned on the outside, and made to'slide in, and be kept tight bypacking rings c c, surrounding the piston, and placed in the middle of the "length of the cylinder. The cylinder, except at the packing-space, is of the usual shape, of sufficient length to a1- low the piston to make its stroke, and furnished with usual ports G C. Besidesthe rings, the piston has a short bearing on either side of them between f and g, and the remainder of the length is counterbored or made larger, and receives the protecting material x w, as shown, the heads, ports, &c., being protected as before; and the piston-rod may be, if desired, on 'the plan shown in Fig.

3. This cylinder is made in two parts, bolted together at the center. One has a space, in

which are the packing-rings c c and springs d d, which press the rings against the piston. A follower, i, holds in the rings, and makes a iiush joint with the cylinder-liange to meet that on the other part, in manner shown. To prevent dividing the cylinder, the rings may be sprimg in before the piston is put in place, or may be put in in segments, hand-holes or other' openings being provided for this purpose, or to set out77 the springs, or examine the packing, as the case may be.- Steam may also be readily .admitted behind the rings to keep them tight, and may have a constant pressure derived from the boiler, or a varying one from'the cylinder, as is usual. Injthis cylinder just described the main body of the steam in the space O, for instance, is neither in contact with nor exposed to radiation from any good conducting-surface. All sides are protected. Very small quantities of steam will leak in beside the piston A, and receive heat by conduction; but suchwill quicklybecome superheated to the temperature of the metal, and stop doing mischief. It is evident that the cylinders, with elongated pis! tons, (represented in Figs. 3, 4, 5, and 6,) may, if desired, be made entirely of the poor conducting or protecting material x .7a.

In Figs. 7, 8, and 9 the cylinder and'piston are represented of the usual form; but all the interior surfaces of the cylinder are lined, and the piston-packin g rubs on the non-conducting covering. v

By the interior surfaces of the cylinder77 I mean the surfaces with which the steam comes 'in contact while in the cylinder. The expression, therefore, is intended to include not only the interior surfaces of the cylinder proper,

but also those of the cylinder-passages, cylinder-heads, and the exposed surfaces of the piston, which, in one sense, forms one side of the cylinder. y i

It is desirable in all cases to exclude the condense-water from the cylinder at every exhaust. This is sometimes done in horizontal engines by making the exhaust-port in the bottom of the cylinder; o r, when the cylinderports answer for both steam and exhaust, they are often put in the` side, with the bottom of the-port level with the bottom of thecylinder.

In Figs. 7 and 9 the ports C C incline from the bottom of the cylinder to the valve-face E.

By this means the water will be carried out of the cylinder by gravity and the force of the exhausting steam.

VWhen the ports C C' make the usual double turn shown in Fig. 8, it is difficult to line them. To obviate this, I have made the valve-face and'part of the ports in a separate plate, M', which meets the cylinder-casting, witha steamtight'joint on the line m. The plate is-bolted fast tothe cylinder through suitable anges, and the steam-chest bolts to the plate in the usual manner.

Itis proposed to make the cylinder, and, if desired, the cylinder-heads, piston, and pistonrod, of a homogeneous material of low conducting-power. Glass cylinders of moderate size may be made in this way. Large cylinders, however, of glass, porcelain, o r other brittle substances, will need strengthening. Figs. l0, 11, 12, and 13 represent plans for ydoing this, X being the cylinder, of low conducting-power.

In Figs. l0 and 1], X is surrounded by a strong cylinder, N, of larger diameter, an annular space a, being left between the two. The heads s ould be of poor conducting material, or lined with it. The ports may be made in the heads, as shown, if desired.

It is proposed to flllthe annular space n v either with cement or an 'elastic substance,

like india-rubber or hemp, compressed suiiiciently to prevent the inner cylinder from bursting. The space rn may also be lilled with steam,

and serve, in some measure, as a steam-jacket, and at the same time resist fracture by a pressure opposite `to thatof `the cylinders.

Again, the space n may be formed into one or more chambers, and iilled with a fluicL-oil, for

instance-and this may receive steam-pressure from any source desired.

By having a series of chambers, as shown in the dotted lines, with small pipes p pp run `ning through the iiuid into them from the cyl-v inder, the varying pressures inside thel noncondueting cylinder will be transmitted to the outside, and there will be little danger of fracture from simple pressure. Of course, steam .direct from the cylinder may be admitted into this chambered jacket; but the outer cylinder in that case had better belined.

In Figs. 12 and 13 the poor conducting cylinder X is hoopedwith strengthening material. `The hoops N N may be placed directly on the cylinder, or have elastic material n interposed.

y It will be observed that aihooped cylinder is simply the mechanicalequivalent of the combination shown in all the figures from 1 to'9,

for, considering the lining as the cylinder proper, the surrounding metal serves like a hoop to strengthen it. l

The following is a list ofthe principal materials which I propose to use for the interior surface of steam or gas engine cylinders, viz: glass, porcelain, and all kinds of potteryware, and the glazing usually applied thereto, enamel, lire clay or brick, alum, mica, asbestus, carbonate and 'sulphate of lime, charcoal and plumbago, bismuth, antimony, lead, German silver, and a compound metal herein after mentioned; also, 'in some cases, wood and vulcanized. india-rubber. All of these substances conduct heat less freely than cast-iron, and for that Vreason theyand other materials, the equivalents thereof in that respect, may be economically used for the purposes specied. y

Glass possesses many qualities which render it specially applicable. It has very low conducting-p ower, thebest kinds are little acted on Y by steam, and its hardness renders it lit for a wearing-surface. It is liable to' crack when the temperature is changed suddenly; but when well annealed small cylinders may be made of it, and used without strengthening. It may be employed with advantagerfor an interior cylinder yon one of the plans shown in Figs. 10 to 13. It may alsol be made in staves or plates, and fitted as a lining to cylinders.

Porcelain, stone, or pottery -ware, fire clay or brick, and phnnbago or crucible material may be used substantially in the same manner as glass.` The glazing put upon most of these substances may be applied to all, and will answer for the wearing-surface.

I have constructed a metal cylinder, the interior surfaces of which are coated with enamel, and it is proposed to make entire cylinders ofthe same material.

Enamel has manyproperties common to both y glass and porcelain, and is used to line cooking-vessels, stationary wash-basins, &c. The ingredients of .many kinds of enamel may be .found in receipt-books, though the business is usually conducted secretly. One kind is co1 nposed of about sixteen parts of redlead mixed with sixteen parts of powdered flint glass and about three partsV of calcined borax. Porcelain-clay is sometimes an ingredient. The materials are thoroughly incorporated by melting. The compound formed is poured into water, and afterward ground to powder.

. The` enamel is applied substantially as follows: The metalis lirst cleaned, and the ground enamel is made int-o apaste with spirits of turpentine or other liquid, and applied to the surfaces. It is then dried, and the whole casting is heated sufficiently to melt the glazing. The cylinder represented in Figs. 7 to 9 may be easily operated .on in this manner, for by removing plate M all parts of the ports become accessible. The castings are sometimes changed in shape by the severe heat required to melt the enamel; but if the plan of construction shown in Figs. 3l to 6 be u'sed this will make little diiference.

When the piston rubs on the enamel, as in Figs. 7 to 9, the cylinder may be bored before the process, and the rubbing-surfaces Vafterward ground, so as to be accurate. -Y

A cylinder may be cut directly out of marble or other stone. 'The scale, which, by its poor conducting property, so injures the evaporative efficiency of steam-boilers, may be applied with advantage to the cylinders by si1n ply heating water in them, which holds in solution sulphate of lime and other salts. `Plaster-of-paris may be cast in plates for linings, or directly on the interior surfaces of the cylinder. Either` marble, chalk, alum, mica, asbestus, oru charcoal, in a powdered state, may be mixed with plaster and operated with in the samemanner, or be pressed in a mold into the proper shape; or one or more of the same may be made into a cement with linseed-oil or equivalent substance, and putl in shape for linings. y y

The simple metals above mentioned may be used, so far as is practicable, for both cylinders and linings. German silver may be employed in a similar manner, and may be sufficiently hardened with antimony to answer for a wearing-surface. I propose to use an alloy or co1n pound metal for both cylinders and linings, composed of seven parts of lead and one of antimony, thehardness bein g varied by slightly changing theproportion of antimony. 'A portion of the antimony may be replaced by bismuth, which will decrease the conductingpower, and not alter the mechanical properties of the compound materially. Though all metals are good conductors compared with glass or other silicate, it may be necessary, in

cylinder absorbs water, which must be heated and cooled at every stroke. Cloth, fur, and porous material, I conclude, can only be used with advantage when the steam is sufficiently superheated to prevent a deposition of Water.-

When the linings are made in sheets or plates they may be secured by screws passing through them, or by Wedges, or in an evident manner, and metal plates may be hammered so as to hold themselves in place, like the staves in an air-pump of a sea-going steamer.

The transmission of heat is retarded by a break in the conductor. It is proposed, therefore, to line some of the surfaces of a steamcylinder with a sheet of metal so thin that it will hold little heat of its own, and the break in the continuity of the conductor will retard heat passing to and om the surrounding` metal, and thus prevent great losses. Such a lining could be set out from the cylinder a little by studs, and thus prevent conduction entirely, and the thin metal would act as a screen to intercept radiant heat. I would not, however, use the space between the lining and .cylinder as a steam-jacket, for that would defeat the very object I have in view, as the metal would thereby be kept hot, not only during the steam but during the exhaust stroke, when lthe heat conducted through it would be carried to waste. I propose to iill the place behind the metal screen either with poor conducting material, which the sheet metal holds in place, or Iwould let the steam'in the cylinder circulate on both sides of the screen, when that next the metal would be superheated and cause injury to that extent; but the main body of the steam would be protected.

I believe that greater economy can be obtained, even in a non-conducting cylinder, Y

with superheated rather than saturated steam, as the superheat will prevent water from lying on the metal surfaces to be heated and cooled at each stroke. I have found that a film of water adheres to the interior surface even of a glass cylinder when saturated steam is used. Single acting and double-cylinder engines should be slightly more economical than the ordinary double-acting engine, even when all the cylinders are protected.

It is anticipated that in some instances it may be impracticable to make the whole interior surfaces of the cylinder of a poor conductor of heat. Nor is this necessary in order to attain economy. The losses occasionedby unprotected surfaces will simply be in some measure proportioned to their extent, and the total gain be less than when the Whole interior is protected. It is not proposed either to make all parts of the interior surfaces in the same way or of the same material. For instance, the cylinder proper may be made entirely of a poor conductor, and the heads be linedwith such, or vice versa.

It is evident that a poor conducting cylinder Will be useful in all engines operated by gases or liquids, which change in temperature while passing through the cylinder.

The principal feature of my invention is the practical discovery that it is economical to construct steam-engine cylinders of a poor conductor of heat. Watt, in his early experiments, tried a wood cylinder, so that it might not be cooled by the condensing water, which was then admitted into the cylinder 5 but he still had the water which remained to heat and cool at every stroke, and abandoned the experiment. By condensing the steam in a separate vessel, he made the great improvement in the steam-engine which immortalized his name. Still, we can now see that he stopped half-way.

Again, glass steam-cylinders are in daily use for toy engines, glass being employed merely because it is transparent. Its real value for steam-engine cylinders is unknown, l

and therefore of no use to the World.

I disclaim glass steam-en gine cylinders when simplyusedbecausetransparent,forinstruction and amusement rather than the attainment of a new effect in the economical performance of the useful work for which steam-engines are generally employed. I have, however, made the new and useful discovery that there is economy in constructing the interior surfaces of a steam-cylinder of a material which conducts heat less freely than that commonly employed, and have devised the means above described to make such discovery of practical benefit.

I claim as new and desire to secure by Letters Patentl. Lining the interior surfaces of the cylinders of engines operated by steam or heated gas with glass, porcelain, enamel, or equivalent substance, in manner substantially as described, to produce the results specified.

2. The combination of the cylinder X with the cylinder N, or its equivalent.

3. The elongated piston A, in combination with the lining or protecting material w x.

4. The combination of the pipe b with the piston-rod or trunk, all substantially as and for the purposes herein set forth.

OHAS. E. EMERY. Witnesses:

H. W. REDFIELD, W. P. TROWBRIDGE. 

